1. Field of the Invention
This invention relates to bleach-containing paste-form detergents and to a process for their production.
2. Discussion of Related Art
Detergents used in the home are tailored to meet domestic requirements. Thus, they are normally powders or are sufficiently liquid to be able to be poured out and dispensed without difficulty. Since even liquid detergents are intended to be stable in storage over relatively broad temperature ranges, additions of organic solvents and/or hydrotropes are often incorporated although they do not make any contribution towards the washing or cleaning result and, for this reason, are undesirable. One way of overcoming possible dispensing problems with detergents having inadequate flow properties is proposed in European patent application EP 253 151 A2. This document describes liquid and, in some cases, highly viscous detergents based on nonionic and anionic surfactants which contain polyethylene glycol as the hydrotrope and which do not have to be dispensed in liquid form by the user, but instead are portion-packed in bags of a water-soluble material, for example polyvinyl alcohol.
The paste-form detergent described in European patent EP 295 525 B1 consists of a phase which is liquid at temperatures below 10.degree. C. and which is formed by nonionic surfactant and of a solid phase dispersed therein which has a certain particle size and which is formed by washing alkalis, sequestering agents and optionally anionic surfactants. The surfactants or surfactant mixtures used are required to have pour points (solidification points) below 5.degree. C. to avoid solidification of the paste at low transportation and storage temperatures. This detergent paste is intended for institutional laundries and is so-free flowing that it can be transported through a suction line by a standard feed pump. However, it has been found that pastes of the type in question are not always able satisfactorily to guarantee the homogeneity of their ingredients during the production process and, in many cases, even tend to separate in storage. This separation involves not only separation of the solid components from the liquid components, but also phase separation of the liquid ingredients.
Another paste-form detergent containing as nonionic surfactant 40 to 70% by weight of ethoxylated C.sub.10-20 fatty alcohol liquid at room temperature with an average degree of ethoxylation of 1 to 8 and 20 to 50% by weight of ethoxylated and propoxylated C.sub.10-20 fatty alcohol liquid at room temperature with an average degree of ethoxylation of 2 to 8 and an average degree of propoxylation of 1 to 6 and 1 to 10% by weight of soap is described in International patent application WO 95109229. This paste-form detergent is so pseudoplastic that it does not flow under the effect of gravity at room temperature, but assumes a much lower viscosity when subjected to shearing and is then able to flow under the effect of gravity. This paste-form detergent is preferably dispensed by applying shear forces to reduce its viscosity so that it is able to flow and can be dispensed by feed pumps.
European patent EP 0 448 581 B1 describes a liquid to paste-form bleach-containing detergent which--based on the detergent as a whole--contains (A) 20 to 35% by weight of a surfactant component consisting of (A1) 1 to 4% by weight of anionic surfactants from the class of sulfonates and soaps present as alkali metal salts and (A2) 16 to 34% by weight of nonionic surfactants having a pour point of at most 10.degree. C., which are alkoxylated linear alcohols or 2-methyl-branched alcohols containing 10 to 18 carbon atoms or mixtures thereof, (B) 10 to 35% by weight of complexing or alkaline earth metal ion-binding builder salts, (C) 15 to 40% by weight of sodium metasilicate, (D) 8 to 25% by weight of bleaching persalts, (E) up to 15% by weight of other detergent ingredients and (F) less than 3% by weight of water, with the proviso that the sum total of components (B+C)=30 to 60% by weight.
The detergents described in the document cited above are highly viscous and have thixotropic properties. Even though the stability of the oxidizing agents incorporated in these detergents is described as adequate, it has been found that their cleaning effect, particularly on bleachable soils, is not satisfactory. It is precisely detergents used as perborate-containing detergents that are required to develop a particularly good bleaching effect so that even bleachable soil such as, for example, food residues and food dyes can be completely removed.
The problem addressed by the present invention was to provide a paste-form detergent which would show high stability in storage and which would contain both oxidizing agents and oxidation-boosting bleach activators so that it would have an excellent bleaching effect on bleachable soil.